1. Field of the Invention
This invention relates generally to the design of a bipolar electrosurgical scissors, and more particularly to a surgical scissors incorporating bipolar electrodes as its blade elements, such that mechanical cutting with subsequent electrocoagulation can be achieved without requiring an instrument exchange.
2. Discussion of the Prior Art
Electrocoagulating instruments include at least one conductive electrode. Radio frequency energy is conducted through this electrode to either a remote conductive body-plate (monopolar) or to a second, closely-spaced conductive electrode (bipolar). Current passing through the gap between the two electrodes will coagulate blood and other body fluids placed between them.
Monopolar electrocautery instruments suffer from the fact that the return path between the active-electrode and the large area body-plate can be unpredictable as the electrical current seeks the return electrode through the path of least resistance. With bipolar electrosurgical instruments, however, because the two electrodes are closely spaced to one another, usually at the distal end of an instrument handle, the return path is very short and only involves the tissue and fluids in the short path between the electrodes.
There is available in the prior art a scissors-type instrument for mechanically snipping tissue during the course of an endoscopic procedure. Such a scissors comprises of pair of blades fabricated from metal and disposed at the distal end of an elongated tubular member whose outside diameter is sufficiently small to allow it to be passed through the working lumen of an endoscope, a laparoscope or other similar devices known in the art. Disposed at the proximal end of the rigid tube is a scissors-type handle having a pair of members, each with a finger-receiving loop therein which are pivotally coupled to one another. An appropriate linkage is made between the handle members and the blades so that manipulation of the handle members will result in an opening and closing of the blades relative to one another. When using a mechanical cutting scissors of this type to excise tissue, when a blood vessel is cut, bleeding results. At that point, it is generally necessary for the surgeon to remove the scissors instrument from the working lumen of the endoscope and then insert an electrocoagulator down the endoscope to the site of the bleeder. This instrument exchange is time-consuming and in a surgical procedure where moments count, it would be desirable to have a scissors-type instrument for cutting but which also incorporates the ability to coagulate blood and other body tissue using RF energy.
There is also available in the prior art monopolar scissors where both of the scissors blades form one pole and with a remote body plate being the second pole. To date, however, there is not available in the marketplace a bipolar electrosurgical scissors where its two blades are electrically isolated from one another and comprise the bipolar electrode pair. With metal-to-metal contact along the sharpened edges of the two blades, an electrical short results. Furthermore, the attempt to use a rivet or screw as the pivot point for the blades is another area where short-circuiting is likely to occur. When such a short exists, the electrical current does not flow through the blood or body tissue to effect coagulation, but instead, follows the short-circuit path from one electrode to the other.
In a copending application, Ser. No. 07/887,212, filed May 26, 1992, there is described a bipolar scissors for insertion into a laparoscope, trocar or endoscope for effecting electrocoagulation of blood and tissue during laparoscopic or other endoscopic surgery. The scissors blades at the distal tip of the instrument perform cutting of the tissue by mechanical shearing action. The two blades are effectively insulated from one another, allowing them to function as bipolar electrodes for electrocoagulating small blood vessels in the surgical field.
The instrument of the aforereferenced application includes a scissors-type handle having first and second pivoting members, each with a finger-receiving loop on one end of each and extending from the opposite end of one is an elongated, rigid tubular member of a size capable of being inserted through the trocar or endoscope. Affixed to the distal end of the rigid tubular member is a first blade composite which comprises a metal blank having a suitable ceramic layer bonded to one major surface thereof, the ceramic being honed to define a sharp cutting edge. Pivotally joined to the first blade by an insulating pivot member is a second blade composite, also having a metal blank with a ceramic substrate bonded to one major surface thereof. When the two blade blanks are pivotally joined together, the ceramic layers are in face-to-face relationship and because the cutting edges thereof are honed, the blades are capable of cutting tissue when made to move in a scissors-like manner with tissue placed between the cutting edges thereof.
Extending through the lumen of the elongated tubular member is a wire or rod which is rigid in the longitudinal direction and which is coupled at its proximal end to one of the handle members and at its other end to one of the scissors blades. By appropriately manipulating the handle members, a snipping action of the blades results.
The instrument further includes means for applying a RF voltage across the gap between the two metal blade blanks which are maintained separated from one another by the ceramic faces bonded to these blanks. As such, the blades of the instrument itself can be used as a bipolar electrocoagulation device, obviating the need for doing an instrument exchange when it is necessary to coagulate blood and tissue following the mechanical cutting thereof.
In copending application Ser. No. 08/092,076, filed Jul. 16, 1993, there is described a bipolar electrosurgical scissors having curved blades in the embodiments of each of the aforereferenced applications, the bipolar blades are constructed by appropriately adhering a specially ground ceramic insulating member defining the sheering surface and cutting edge of the scissors to metal electrodes where it is the ceramic surfaces that interact with one another to perform the cutting function as the blades are opened and closed relative to one another. While that arrangement works well in implementing a bipolar electrosurgical scissors, the cost of manufacture is relatively high because of the difficulty in working with ceramics, especially when constructing electrosurgical scissors having arcuate blades. Those skilled in the art appreciate that ceramic will readily fracture when subjected to bending forces and, hence, it is necessary to produce the requisite ceramic elements for the scissors in a series of grinding operations.
A need therefore exists for a bipolar electrosurgical scissors for use in both open and endoscopic surgical procedures where the shearing surfaces may be surgical steel, but where the blades can also be used in performing bipolar electrocoagulation as the cutting progresses.